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Derivatives - Net Gain (Loss) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Derivative [Line Items] |  |  |  |
Derivative, (loss) gain on derivative, net | $ (63.3) | $ 3.7 | $ (161.4) | $ 7.5
Commodity contract [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Derivative, (loss) gain on derivative, net | (63.6) | 2.9 | (159.6) | 11.8
Commodity contract [Member] | Glencore [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Derivative, (loss) gain on derivative, net | (28.7) | (7.9) | (53.5) | 4.7
Foreign exchange contract [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Derivative, (loss) gain on derivative, net | $ 0.3 | $ 0.8 | $ (1.8) | $ (4.3)

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5618551-113959 + Details
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